diff --git a/jest.config.ts b/jest.config.ts
index 889f7dfc..0f491169 100644
--- a/jest.config.ts
+++ b/jest.config.ts
@@ -8,7 +8,7 @@ const defaultEsmPreset = createDefaultEsmPreset();
 const config: Config = {
   testEnvironment: 'node',
   testMatch: ['<rootDir>/test/**/*-test.ts'],
-  setupFiles: ['<rootDir>/test/jest.setup.ts'],
+  setupFiles: ['<rootDir>/test/jest.setup.cjs'],
   ...defaultEsmPreset,
   moduleNameMapper: {
     '^(\\.{1,2}/.*)\\.js$': '$1',
diff --git a/test/jest.setup.ts b/test/jest.setup.cjs
similarity index 51%
rename from test/jest.setup.ts
rename to test/jest.setup.cjs
index 99141b16..82c48591 100644
--- a/test/jest.setup.ts
+++ b/test/jest.setup.cjs
@@ -1,6 +1,6 @@
-import os from 'node:os';
-import sinon from 'sinon';
+const os = require('node:os');
+const sinon = require('sinon');
 
-export default function () {
+module.exports = function () {
   sinon.stub(os, 'EOL').value('\n'); // Stub os.EOL to always be '\n' for testing/snapshot purposes.
-}
+};